Digitizer systems are used as input devices for a variety of Human Interface Devices (HIDs) and for a variety of different applications. A touch-screen is one type of digitizer system that is integrated with a Flat Panel Display (FPD). Touch-screens are used for operating portable devices, such as laptop computers, tablet computers, MP3 players, smart phones and other devices.
Digitizer systems track free style input provided with a finger and/or stylus. A digitizer system typically includes a digitizer sensor such as a grid based capacitive sensor and a circuit to operate the sensor. A grid based capacitive sensor may be operated by the circuit for mutual capacitive or self-capacitive detection and may also be picked up on grid lines of the sensor and tracked. The circuit may determine coordinates of the finger and/or stylus based on output detected and report the coordinates to a processor of an HID.
It is known for a user to apply a cover film such as a protective film or privacy film over a display surface of a touch-screen and to provide the free-style input over the cover film. Protective films are typically applied to protect the display surface against scratches, dust and glare from sun or bright light. Privacy films are typically applied to prevent others from stealing sideways glances at content on the display. Cover films such as protective films and privacy films applied on touch-screens may range in thickness as well as material based on their intended function as well as the size of the display on which they are applied.